{"references": ["C.Onan, O. Kucur, and E. Ozturk, \"Performance of quasi-synchronous\nscale-time-code division multiple access system over the additive white\nGaussian noise channel\", IEEE Signal Processing and Communications\nApplications Conference, pp.708-711, April 2004.", "A. Kuramoto, T. Abrao, and P. J. Jeszensky. \"Sets of sequences for\nQS-CDMA systems with interference cancellation over multipath\nRayleigh fading channels\", IEEE Eighth International Symposium on\nSpread Spectrum Techniques and Applications, pp.694-698, Sep. 2004.", "J. K. Kyeong, R. A. Iltis, \"Joint detection and channel estimation\nalgorithms for QS-CDMA signals over time-varying channels\", IEEE\nTrans.on Commun., Vol.50, pp. 845-855, May 2002.", "S. Cioni, G. D. Gaudenzi, and R. Rinaldo, \"Adaptive coding and\nmodulation for the reverse link of broadband satellite networks\", IEEE\nGLOBECOM '04, Vol.2, pp. 1101-1105, Dec. 2004.", "F. Pingzhi, \"New direction in spreading sequence design and the related\ntheoretical bounds\", IEEE International Conference on Communications,\nCircuits and Systems and West Sino Expositions, Vol.1, pp. xliii - xlviii,\nJuly 2002", "S. H. Duan. \"Researches on Quasi-Synchronous CDMA and Its\nApplication in Mobile Satellite Communication System\". Harbin Industry\nUniversity, 2001.", "L. Biqi; Z. Ping, H.Jiandong, \"A generalized QS-CDMA system and the\ndesign of new spreading codes\", IEEE Trans.on VTC, Vol. 47, pp.12687-\n1275, Nov.1998", "S. Stanczak, A. Feistel, \"Dynamic resource allocation for\nfrequency-selective orthogonal QS-CDMA channels\", IEEE Conference\non Signals, Systems and Computers, Vol. 1, pp.632-636.2004", "J. K. Kyeong, R. A. Iltis, \"Block coded modulation for the QS-CDMA\nsystem\", IEEE Conference on Signals, Systems and Computers, Vol. 1,\npp.9-12, Nov. 2003\n[10] D. V. Sarwate, \"Mean-Square Correlation of Shift-Register Sequence\",\nIEE Proceedings.1984,131(2):101-106."]}

In the paper, the performance of quasi-synchronous CDMA (QS-CDMA) system, which can allow an increased timing error in synchronized access, is discussed. Average BER performance of the system is analyzed in the condition of different access timing error and different asynchronous users by simulation in AWGN channel. The results show that QS-CDMA system is shown to have great performance gain over the asynchronous system when access timing error is within a few chips and asynchronous users is tolerable. However, with access timing error increasing and asynchronous users increasing, the performance of QS-CDMA will degrade. Also, we can determine the number of tolerable asynchronous users for different access timing error by simulation figures.